The present invention pertains to dispensing systems for flowable material, and more particularly to curable liquid dispensing systems used to accurately place small amounts of curable liquid, such as adhesive.
In applications such as the electronics and fiber optics industries, it is necessary to join items using a very small volume of adhesive, often as small as 1 microliter, 1 nanoliter, or even less. Because the placement of items to be bonded is typically critical, such applications generally require a fast curing adhesive, such as two-part epoxy. The curable liquid may be dispensed by syringe-type applicators, utilizing manually actuated plungers, or by applicators having air actuated pistons for accurately dispensing precise amounts of curable liquid. The applicators may be hand-held for manual placement of curable liquid on a desired surface or they may be incorporated into automated curable liquid dispensing systems.
Syringe-type applicators have included an elongated barrel which serves as both a reservoir for the curable liquid and as a handle allowing the user to grasp and manipulate the applicator. The reservoirs of these syringe-type applicators are generally available with capacities as low as about 3 cc (cubic centimeters). However, they are used manually to dispense very minute amounts in successive bonding applications, for example, using magnifiers such as microscopes. Each of these minute dispensing operations takes time to ensure accuracy and may each result in depleting the reservoir by only 1 microliter (0.001 cc) or even 1 nanoliter (0.000001 cc). Thus, before depleting the entire 3 cc reservoir, a significant amount of curable liquid may cure within the reservoir. This pre-dispense curing is especially problematic with fast curing adhesives, such as two-part epoxies, and results in wasted curable liquid and, therefore, additional expense.
There is a need for a device that can dispense very small and precise amounts of curable liquid while preventing the waste of curable liquid due to pre-dispense curing.
The present invention provides a curable liquid dispensing pen which may be used to dispense very low volumes of curable liquid while reducing the amount of pre-dispense cured liquid, as compared to previously available curable liquid dispensers. The dispensing pen is particularly suited to very low volume dispensing of fast curing two-part epoxies and is configured to permit manual placement of curable liquids. Alternatively, the dispensing pen may be used with automated curable liquid placement equipment.
The invention has various aspects, but in one exemplary embodiment, the curable liquid dispensing pen of the present invention includes a pen body to which a curable liquid dispensing reservoir may be removably mounted. The pen body holds the reservoir so that the reservoir may be sized to accommodate a small volume of curable liquid, such as an amount which could be dispensed in successive dispensing operations without allowing a significant amount of the curable liquid to cure in the reservoir. For example, the reservoir may be sized to contain about 0.25 cc of curable liquid.
The reservoir is mounted to the pen body by a connecting element which is coupled to one end of the pen body. In an exemplary embodiment, the connecting element may be screwed onto the end of the pen body and has a slot which receives a flange on the reservoir. As the connecting element is screwed onto the pen body, the reservoir is brought in sealing engagement with the pen body. In this embodiment, the pen body further includes O-rings which engage the reservoir and the connecting element.
The pen body is configured to be attached to a source of compressed or pressurized air and has a passage which directs the pressurized air to the reservoir mounted on the pen body. The reservoir has an interior which contains the curable liquid. A piston within the reservoir forces curable liquid from the cavity and through an outlet tube under the action of the pressurized air. In an exemplary embodiment, a controller regulates the duration and pressure of a pulse of air acting on the piston so that the movement of the piston may be accurately controlled to dispense a precise amount of curable liquid.
In another aspect of the invention, a curable liquid dispensing reservoir is configured to be removably attached to a curable liquid dispensing pen. The dispensing reservoir generally includes a reservoir body having an interior containing a curable liquid, a first end, a second end having an opening, and a flange surrounding the opening. The flange is configured to couple with the dispensing pen in a releasable manner. An elongate tube having an inlet and an outlet is coupled with the reservoir body such that the inlet is in fluid communication with the reservoir body interior. The outlet is adapted to dispense the curable liquid. A piston is positioned for movement within the interior with the curable material being on one side of the piston and the opening being on an opposite side of the piston. The piston is moved by pressurized air introduced through the opening on the opposite side of the piston to urge the curable liquid from the outlet. Preferably, a stop member, such as an annular ring, is provided proximate the opening and retains the piston within the interior.
These and other features, advantages and objectives of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings.